Method for fabricating a damascene self-aligned ferrorelectric random access memory (f-ram) with simultaneous formation of sidewall ferroelectric capacitors

ABSTRACT

A method for fabricating a non-volatile, ferroelectric random access memory (F-RAM) device is described. In one embodiment, the method includes forming an opening in an insulating layer over a surface of a substrate, and forming bottom electrode spacers proximal to sidewalls of the opening. Next, a ferroelectric dielectric layer is formed in the opening over the surface of the substrate and between the bottom electrode spacers, and a pair of top electrodes is formed within the opening comprising first and second side portions displaced laterally from respective ones of the bottom electrode spacers by the ferroelectric dielectric layer.

CROSS REFERENCE TO RELATED PATENT APPLICATIONS

The present application claims priority from U.S. Provisional PatentApplication Ser. No. 61/522,960 filed Aug. 12, 2011, the disclosure ofwhich is herein specifically incorporated by this reference in itsentirety. The present invention is also related to the subject matterdisclosed in United States patent application Serial Nos. [RAM 626] for“Method for Fabricating a Damascene Self-Aligned Ferroelectric RandomAccess Memory (F-RAM) Device Structure Employing Reduced ProcessingSteps” and [RAM 628] for “Method for Fabricating a DamasceneSelf-Aligned Ferroelectric Random Access Memory (F-RAM) Having aFerroelectric Capacitor Aligned with a Three Dimensional TransistorStructure”, both filed on even date herewith and assigned to RamtronInternational Corporation, the disclosures of which are also hereinspecifically incorporated by this reference in their entirety.

BACKGROUND OF THE INVENTION

The present invention relates, in general, to the field of integratedcircuit (IC) memory devices. More particularly, the present inventionrelates to the field of non-volatile, ferroelectric random access memory(F-RAM) devices and a method for fabricating the same in the form of adamascene self-aligned F-RAM that allows for the simultaneous formationof two sidewall ferroelectric capacitors.

According to World Semiconductor Trade Statistics (WSTS), thesemiconductor market reached an important milestone in 2010, postingworldwide revenues of more than $300 billion (in United States dollars)for the first time in the industry's history. In particular, the memorychip segment exhibited the highest growth rate during 2010, increasingfrom $45 billion in 2009 to $71 billion in 2010, representing a 57%year-over-year growth rate. Embedded memory devices represented morethan 23% of the overall semiconductor market in 2010.

Within this context, the increasing demand for higher processing poweris driving the semiconductor industry to develop memory devices withhigher operational speeds in order to support the capabilities of modernelectronic devices. F-RAM has emerged as a promising option for theindustry, particularly in the market areas of mobile computing, smartmeters, radio frequency identification (RFID) devices, office equipmentand other applications requiring non-volatile data storage.

Standard dynamic random access memory (DRAM) and static random accessmemory (SRAM) devices, while providing relatively fast access times, areconsidered to be volatile memory devices inasmuch as data stored in suchmemories is lost when power is interrupted. In contrast, non-volatilememory devices are those that function to retain data despite any lossof power.

F-RAM devices are inherently non-volatile, meaning that these memorydevices are able to retain stored data while the device is not powered.In comparison to electrically erasable programmable read only memory(EEPROM) FLASH memory devices, which are currently the most popular typeof non-volatile memory, F-RAM devices have several advantages includinglower power requirements (operational voltages of just 5V needed duringread-write operations), higher read-write speeds (less than 70nanoseconds), and virtually unlimited write endurance capability (morethan 10,000,000,000 write cycles.

F-RAM memory devices may be fabricated based on the use of leadzirconium titanate (PZT) ferroelectric storage capacitors as memoryelements integrated with complementary metal oxide semiconductor (CMOS)addressing, selection, and control logic. PLZT is a Lanthanum-doped formof PZT wherein some of the lead is replaced with lanthanum.

It is also known that PZT may also be doped with strontium and calciumto improve its ferroelectric dielectric properties. Ferroelectricstorage capacitors having a strontium bismuth tantalate (SBT); bariumstrontium titanate (BST); and strontium titanate oxide (STO) dielectricsare also known in the art.

As used in the present application, the term “PZT” shall also beconsidered to include PLZT, SBT, BST, STO and other comparableferroelectric dielectric materials. Further, it should be noted that thetechniques of the present invention disclosed herein are applicable toall known ferroelectric dielectrics including Perovskites and layeredPerovskites (whether doped or undoped) including PZT, PLZT, BST, SBT,STO and others while simultaneously allowing for a potentially broaderchoice of electrode materials and the use of a forming gas annealprocess step on the completed IC structure.

Regardless of the ferroelectric dielectric material employed, inoperation F-RAM devices function through their ability to be polarizedin one direction or another in order to store a binary valuerepresentative of a logic level “one” or “zero”. The ferroelectriceffect allows for the retention of a stable polarization state in theabsence of an applied electric field due to the alignment of internaldipoles within the Perovskite crystals in the dielectric material. Thisalignment may be selectively achieved by application of an electricfield which exceeds the coercive field of the material. Conversely,reversal of the applied field reverses the internal dipoles.

A hysteresis curve, wherein the abscissa and ordinate represent theapplied voltage (“V”) and resulting polarization (“Q”) statesrespectively, may be plotted to represent the response of thepolarization of a ferroelectric capacitor to the applied voltage. A morecomplete description of this characteristic hysteresis curve isdisclosed, for example, in U.S. Pat. Nos. 4,914,627 and 4,888,733assigned to Ramtron International Corporation, assignee of the presentinvention, the disclosures of which are herein specifically incorporatedby this reference.

Representative of the current state of the art in F-RAM devicefabrication is that disclosed in U.S. Pat. No. 6,150,184 for: “Method ofFabricating Partially or Completely Encapsulated Top Electrode of aFerroelectric Capacitor,” also assigned to Ramtron InternationalCorporation. Therein described is the structure of a ferroelectriccapacitor that includes a bottom electrode, a top electrode, an aferroelectric layer located between the top and bottom electrodes thatextends to completely encapsulate the top electrode, except for acontact hole to allow metallization of the top electrode. The totalencapsulation of the top electrode reduces the sensitivity of theferroelectric capacitor to hydrogen and thus improves electricalswitching performance. The encapsulation technique can also be used toimprove the performance of ferroelectric integrated circuits and otherdevices.

Further representative of the state of the art in the fabrication ofF-RAM devices is that disclosed in U.S. Pat. No. 6,613,586 for:“Hydrogen Barrier Encapsulation Techniques for the Control of HydrogenInduced Degradation of Ferroelectric Capacitors in Conjunction withMultilevel Metal Processing for Non-Volatile Integrated Circuit MemoryDevices,” also assigned to Ramtron International Corporation. Thereindescribed is a device structure which ameliorates the hydrogen induceddegradation of ferroelectric capacitors by completely encapsulating thecapacitor within a suitable hydrogen barrier material, such as chemicalvapor deposition (“CVD”) or sputtered silicon nitride (Si₃N₄), thusensuring process compatibility with industry standard process steps.Although the deposition process for CVD Si₃N₄ itself contains hydrogen,the deposition time may be kept relatively short thereby allowing thetitanium nitride (TiN) local interconnect layer to act as a “short term”hydrogen barrier.

The disclosures of U.S. Pat. Nos. 6,150,184 and 6,613,586 are hereinspecifically incorporated by this reference in their entirety.

Despite the aforementioned advantages over volatile memory devices andother non-volatile technologies, F-RAMs currently account for arelatively small share of the non-volatile memory device market.Competitively, the main limitation of the F-RAM technology has been itslower storage density compared to FLASH devices coupled with highermanufacturing costs. These limitations stem primarily from the generallycomplex structure of current F-RAM devices which results in amanufacturing process that requires a high number of processing masksand etching steps.

As such, in order to be more competitive in the current memory devicemarketplace and be usable in a wider range of modern electronic devices,F-RAM devices need to be more highly integrated, implying increasedstorage densities and reduced manufacturing costs.

It would, therefore, be highly advantageous to simplify the structure ofF-RAM devices with the purpose of improving storage densitycapabilities. It would also be highly advantageous to reduce the numberof imaging materials and etching steps during F-RAM fabrication in orderto reduce manufacturing costs.

SUMMARY OF THE INVENTION

Disclosed herein is a method for forming a damascene self-alignedferroelectric RAM (F-RAM) device comprising two sidewall ferroelectriccapacitors in an oxide trench coupled to contact studs at the bottom andtop electrodes and isolated by a PZT layer. The fabrication methodcomprises the steps of forming, on a planar surface of a semiconductorsubstrate, three CVD tungsten, titanium/titanium nitride contact studs,followed by the deposition of an oxide layer which is etched based onthe pattern established by a non-erodible mask, forming an opening forthe F-RAM construction, deposition and etching of a titanium aluminumnitride conformal layer to form spacers, deposition and etching of aplatinum bottom electrode layer, application of a photoresist materialto form an image opening to etch the sidewalls of the oxide trench,followed by the deposition of a ferroelectric conformal layer ideallydoped with lead zirconium titanate (PZT) and deposition and etching of aplatinum top electrode layer on top, followed by the formation of threeCVD tungsten, titanium/titanium nitride contact studs, two of them aboveeach of the sidewall capacitors, and application of chemical mechanicalpolishing (CMP) to planarize the surface of the F-RAM structure.Efficiency is enhanced by the formation of a third contact stud usingthe same conformal metal deposition of the fundamental deposition layer.

Also further disclosed herein is a method for forming a semiconductordevice on a substrate having at least two contact studs formed in aplanar surface thereof comprising forming an insulating layer overlyingthe planar surface and selectively removing a portion of the insulatinglayer and a selected portion of the planar surface to form an openingextending to and partially between the at least two contact studs. Firstspacers are formed adjoining sides of the opening over the at least twocontact studs and bottom electrode spacers are formed, each contactingrespective ones of the at least two contact studs in the openingadjoining the first spacers. An insulating cap is formed in the openingbetween the at least two contact studs and the bottom electrode spacersand a ferroelectric dielectric layer is formed in the opening over theinsulating layer, the insulating cap and between the bottom electrodespacers. A pair of top electrodes are formed within the openingcomprising first and second side portions displaced laterally fromrespective ones of the bottom electrode spacers by the ferroelectricdielectric layer. An additional insulating layer is formed between thetop electrodes and over the ferroelectric dielectric layer and first andsecond contacts to each of the top electrodes are formed within theadditional insulating layer.

Still further disclosed herein is a method for forming a ferroelectricdevice comprising forming first and second contact studs in a planarsurface of a substrate and depositing an oxide layer on the planarsurface. The oxide layer is selectively etched to form an openingthrough the oxide layer to first and second contact studs and anover-etched region therebetween and a titanium aluminum nitride layer isdeposited over the oxide layer and within the opening and over-etchedregion. Portions of the aluminum nitride layer are selectively removedexcept for sidewalls of the opening adjoining the first and secondcontact studs to produce first spacers and a noble metal layer isdeposited within the opening. The noble metal layer is selectivelyremoved over the first and second contact studs and within theover-etched region to produce bottom electrode spacers medially of thefirst spacers and an additional oxide layer is deposited within theopening. The additional oxide layer is selectively removed to produce atrench cap in a lower portion of the opening and within the over-etchedregion and a ferroelectric dielectric layer is deposited over the oxidelayer, the trench cap and medial and distal portions of the first andbottom electrode spacers within the opening. An additional noble metallayer is deposited over the ferroelectric dielectric layer andselectively removed to form a pair of top electrodes within the openingand displaced from the bottom electrode spacers by the ferroelectricdielectric layer. An additional oxide layer is deposited over theferroelectric dielectric layer and between the top electrodes andselectively etched to form first and second openings to correspondingtop portions of the pair of top electrodes. Electrical contacts areformed to the first and second end portions through the first and secondopenings.

Additionally disclosed herein is a ferroelectric device which comprisesfirst and second contact studs formed upon a semiconductor substrate anda trench cap extending between the first and second contact studs at aplanar surface of the substrate. First spacers contact each of the firstand second contact studs and extend distally therefrom. Bottom electrodespacers contact each of the first and second contact studs and extenddistally therefrom, medially adjoining the first spacers. Aferroelectric layer overlies the trench cap and the bottom electrodespacers. A pair of top electrodes are disposed within the ferroelectriclayer over the trench cap and medially of the bottom electrode spacersdisplaced by the ferroelectric layer. First and second electricalcontacts are coupled to distal end portions of the pair of topelectrodes.

BRIEF DESCRIPTION OF THE DRAWINGS

The aforementioned and other features and objects of the presentinvention and the manner of attaining them will become more apparent andthe invention itself will be best understood by reference to thefollowing description of a preferred embodiment taken in conjunctionwith the accompanying drawings, wherein:

FIG. 1 is a partial, cross-sectional illustration of the structure of anF-RAM substrate, which provides a depiction of the first-level F-RAMsubstrate with contact studs;

FIG. 2 is a follow-on view which illustrates the non-erodible maskstructure;

FIG. 3 is a follow-on view which illustrates the over-etched regionstructure;

FIG. 4 is a follow-on view which illustrates the structure of the F-RAMopening after the non-erodible mask is removed;

FIG. 5 is a follow-on view which illustrates the conformal CVD titaniumaluminum nitride structure;

FIG. 6 is a follow-on view which illustrates the F-RAM structure withtitanium aluminum nitride spacers;

FIG. 7 is a follow-on view which illustrates the F-RAM structure withetched titanium aluminum nitride spacers;

FIG. 8 is a follow-on view which illustrates the platinum structure;

FIG. 9 is a follow-on view which illustrates the F-RAM structure withplatinum BE spacers;

FIG. 10 is a follow-on view which illustrates the F-RAM structure afterthe etching of the platinum BE spacers;

FIG. 11 is a follow-on view which illustrates the photoresistapplication structure;

FIG. 12 is a follow-on view which illustrates the etched photoresiststructure;

FIG. 13 is a follow-on view which illustrates the trench cap structure;

FIG. 14 is a follow-on view which illustrates the exposed trench capstructure;

FIG. 15 is a partial top plan view which illustrates the F-RAM openingstructure after the deposition of titanium aluminum nitride spacers andbottom electrode layer;

FIG. 16 is a follow-on view which illustrates the etched platinum BEspacers structure;

FIG. 17 is a follow-on view which illustrates the etched titaniumaluminum nitride BE spacers structure;

FIG. 18 is a follow-on view which illustrates the F-RAM openingstructure after the etching of sidewalls;

FIG. 19 is a partial cross-sectional view which illustrates the F-RAMPZT structure;

FIG. 20 is a follow-on view which illustrates the F-RAM structure withplatinum TE spacers;

FIG. 21 is a partial top plan view which illustrates the F-RAM openingafter the deposition of the PZT layer and top electrode layer;

FIG. 22 is a follow-on view which illustrates the etched platinum TEspacers structure;

FIG. 23 is a follow-on view which illustrates the sidewall capacitorstructure;

FIG. 24 is a partial cross-sectional view which illustrates the contactnon-erodible mask structure;

FIG. 25 is a follow-on view which illustrates the contact oxide etchingstructure;

FIG. 26 is a follow-on view which illustrates the photoresist maskstructure;

FIG. 27 is a follow-on view which illustrates the etched oxidestructure;

FIG. 28 is a follow-on view which illustrates the F-RAM contact openingstructure;

FIG. 29 is a follow-on view which illustrates the final F-RAM contactstud structure; and

FIG. 30 is a partial top plan view which illustrates the final F-RAMcontact stud structure.

DESCRIPTION OF A REPRESENTATIVE EMBODIMENT

The present invention presents a novel, non-volatile, ferroelectricrandom access memory (F-RAM) device and a method for fabricating thesame in the form of a damascene self-aligned F-RAM device comprising aPZT capacitor built on the sidewalls of an oxide trench, while allowingfor the simultaneous formation of two ferroelectric sidewall capacitors.

A representative method in accordance with the present inventioncomprises the processing steps disclosed in FIGS. 1 through 30inclusive.

With reference now to FIG. 1, the structure of an F-RAM substrate 100 isshown and provides a depiction of the first-level F-RAM substrate withthree contact studs. A layer of BSPG 102 (boron phosphorus siliconglass) is deposited and planarized onto a silicon or other substrate(not shown in FIG. 1). Any oxide, nitride, or other appropriatedielectric can be substituted for the BPSG 102 layer. In the BPSG 102layer, a non-erodible mask (such as AL₂O₃ or Si₃N₄, not shown in FIG. 1)is employed to reactive-ion etch (RIE) and form contact holes A, B, andC (not shown in FIG. 1). After removing the non-erodible mask, Ti/TiN106 (titanium/titanium nitride) liners and CVD (chemical vapordeposition) tungsten (W) 104 are deposited. A chemical mechanicalpolishing (CMP) operation is then used to planarize back the CVDTungsten 104 and Ti/TiN 106 to the level of the planar surface 108 ofBPSG 102 layer to form contact stud A 110, contact stud B 112, andcontact stud C 114.

With reference additionally now to FIG. 2, a non-erodible mask structure200 is illustrated depicting the chemical vapor deposition (CVD) of aplanarized oxide 202 layer over the top of the F-RAM substrate 100. Theoxide 202 layer is planar as it is deposited over the planarized surfaceof BSPG 102. A non-erodible mask 204 (such as AL₂O₃ or Si₃N₄) issubsequently applied over contact stud C 114 and is defined overportions of contact stud B 112 and contact stud A 110. Masking isperformed by defining the mask layer over the oxide 202 layer and thenusing photoresist to define the desired pattern.

Photoresist is a light sensitive material that when exposed to lightforms a defined pattern on the non-erodible mask 204 as shown in FIG. 2.When the non-erodible mask 204 is etched and the photoresist removed inan O₂ plasma ash, it leaves an exposed surface on the oxide 202 layer.The non-erodible mask 204 can be made of different materials such asaluminum oxide (Al₂O₃), silicon nitride (Si₃N₄), and other metals suchas aluminum. As such, the process disclosed herein allows for the use ofdifferent types of non-erodible mask materials.

With reference additionally now to FIG. 3, the structure of theover-etched region structure 300 is shown. In FIG. 3, the exposedsurface of the oxide 202 layer in the non-erodible mask structure 200 isthen etched down to the planar surface 108 with a reactive-ion etching(RIE) process using, for example, CF₄ in oxygen.

With reference additionally now to FIG. 4, the F-RAM opening structure400 is shown. In FIG. 4, the reactive-ion etching process continues downto the level of an over-etch required across the wafer, wherebyover-etched region 404 is formed below the planar surface 108. Theetching process on oxide 202 in FIG. 4 results in F-RAM opening 402.

With reference additionally now to FIG. 5, the CVD titanium aluminumnitride structure 500 is shown. In FIG. 5, a layer of about 1000angstroms of titanium aluminum nitride film is subsequently deposited bya CVD system over the F-RAM opening structure 400, forming a conformaltitanium aluminum nitride 502 layer on the top of the oxide 202 layerand on the sides and bottom of the F-RAM opening 402. Titaniumtetrachloride (TiCl₄), dimethylethylamine alane (DMEAA) and ammonia gasmay be used as source gases for the CVD of titanium aluminum nitride.

With reference additionally now to FIG. 6, the removal of a portion ofthe titanium aluminum nitride conformal layer creating F-RAM structurewith titanium aluminum nitride spacers 600 is depicted. In FIG. 6, aportion of the conformal titanium aluminum nitride 502 layer is removedfrom the top and bottom of the oxide 202 layer using a reactive-ion etchtechnique. This etching process forms the titanium aluminum nitridespacers 602 on the sides of the F-RAM opening 402. This particular step,however, also produces titanium aluminum nitride stringers 604 in thebottom of the over-etched region 404.

With reference additionally now to FIG. 7, the etching of a portion ofthe titanium aluminum nitride spacers to create F-RAM structure withetched titanium aluminum nitride spacers 700 is depicted. Following theprocess in FIG. 7, reactive-ion etching continues in order to accomplishthe removal of the titanium aluminum nitride stringers 604, producingstring clearing 702 region in the bottom of the over-etched region 404.This reactive-ion etch step also removes a small portion from the top ofthe titanium aluminum nitride spacers 602, forming over-etched region704.

With reference additionally now to FIG. 8, the formation of F-RAMplatinum structure 800 is shown. In FIG. 8, a conformal layer ofplatinum of about 500 to 1000 angstroms is deposited by chemical vapordeposition over the top of the F-RAM structure with etched titaniumaluminum nitride spacers 700, forming the platinum 802 bottom electrodelayer. This platinum 802 bottom electrode layer covers the top andbottom of the oxide 202 layer and sidewalls of the titanium aluminumnitride spacers 602. While platinum is used for the bottom electrode(BE) layer, other known materials compatible with ferroelectric filmscould also be used, including, for example, iridium (Ir) and iridiumoxide (IrOx), palladium (Pd) and palladium oxide (PdOx), ruthenium (Ru)and ruthenium oxide (RuOx), rhodium (Rh) and rhodium oxide (RhOx).

With reference additionally now to FIG. 9, the removal of a portion ofthe platinum 802 bottom electrode (BE) layer in the F-RAM platinumstructure 800 is shown creating F-RAM structure with platinum BE spacers900. In FIG. 9, the platinum 802 BE layer is etched away from the topand bottom of the oxide 202 layer, using a reactive-ion etch process,forming platinum BE spacers 902. Note that in this process step, theplatinum BE spacers 902 are etched below the level of the oxide 202layer, but not to the same height as the titanium aluminum nitridespacers 602, creating an excess of material 904 on top of the platinumBE spacers 902. Platinum is typically etched using a reactive-ion etchusing, although other gases may be used. Ion milling can be used as wellas an alternative etching technique. As illustrated in FIG. 9, theetching of the platinum 802 BE layer creates platinum stringers 906 inthe over-etched region 404.

With reference additionally now to FIG. 10, the etching of a portion ofthe platinum BE spacer layer to create F-RAM structure 1000 isillustrated. In FIG. 10, the application of reactive-ion etch continuesin order to accomplish the removal of the platinum stringers 906,creating string clearing 1002 in the bottom of the over-etched region404. This reactive-ion etching step also removes the excess of material904 from the top of the platinum BE spacers 902, creating a levelsurface 1004 out of the platinum BE spacers 902 layer and the titaniumaluminum nitride spacers 602 layer.

With reference additionally now to FIG. 11, the application of a CVDoxide layer and a photoresist material on the top F-RAM structure 1000is depicted, forming photoresist application structure 1100. In FIG. 11,a conformal oxide 1102 layer is deposited using a CVD process over thetop of the F-RAM structure 1000. A photoresist 1104 material issubsequently spun applied over the top of the oxide 1102 layer, fillingthe F-RAM opening 402 (FIG. 4).

With reference additionally now to FIG. 12, the removal of thephotoresist material in photoresist application structure 1100 is shown,creating etched photoresist structure 1200. In FIG. 12, a portion of thephotoresist 1104 material is etched away using a plasma oxygen (O₂)plasma ash in order to shape a structure below the surface of the oxide1102 layer, leaving the photoresist 1104 material in the F-RAM opening402.

With reference additionally now to FIG. 13, the removal of a portion ofthe oxide 1102 layer in the etched photoresist structure 1200 is shownto create trench cap structure 1300. In FIG. 13, the oxide 1102 layer isreactive-ion etched down to the base of the photoresist 1104 material,by means of a timed etch, forming a trench cap 1302 composed of theremaining oxide 1102 layer.

With reference additionally now to FIG. 14, the removal of the remainderof the photoresist material in the trench cap structure 1300 is shown,forming the exposed trench cap structure 1400. In FIG. 14, thephotoresist 1104 material is completely removed by the same O₂ plasmaash process described above, exposing the trench cap 1302 surface. Notethat the trench cap 1302 (composed of oxide) completely fills theover-etched region 404. In addition, the non-erodible mask 204 isremoved by employing an ion etch chemistry, specific to the type ofmaterials used in the non-erodible mask itself. For example, if thenon-erodible mask is made of Si₃N₄, it may be etched by a Si₃N₄chemistry that will not affect the oxide 202 layer.

With reference additionally now to FIG. 15, a top plan view of the F-RAMopening structure 1500 is shown. From a top view perspective, FIG. 15illustrates contact stud A 110 on the left and contact stud B 112 on theright of the F-RAM opening 402. FIG. 15 also depicts the Ti/TiN 106liners in contact stud A 110 and contact stud B 112, and the CVDtungsten 104 filling both contact stud A 110 and contact stud B 112.Notice also in FIG. 15, the titanium aluminum nitride spacers 602 andplatinum BE spacers 902 are around the sidewalls of the F-RAM opening402. On top of the F-RAM opening 402 structure, a photoresist 1502material is applied and then imaged to form image opening 1504.

With reference additionally now to FIG. 16, the etching of the platinumaround the sidewalls on the F-RAM opening structure 1500 is depicted tocreate etched platinum BE spacers structure 1600. In FIG. 16, using thepattern defined by the image opening 1504, the exposed surfaces aroundthe sidewalls of the F-RAM opening 402 are wet etched away producingundercut regions 1602.

With reference additionally now to FIG. 17, the etching of the titaniumaluminum nitride on the etched platinum BE spacers structure 1600 isshown, forming etched titanium aluminum nitride spacers structure 1700by which the sidewalls of platinum BE spacers 902 are removed. In FIG.17, employing the same pattern defined by the image opening 1504, aportion of the titanium aluminum nitride spacers 602 around thesidewalls of the F-RAM opening 402 is isotropically etched away, formingover-etched regions 1702. Note that the titanium aluminum nitridespacers 602 are etched back to the same level as the platinum BE spacers902.

With reference additionally now to FIG. 18, the removal of thephotoresist material from the titanium aluminum nitride spacersstructure 1700 is shown, creating F-RAM opening structure 1800. In FIG.18, the remaining photoresist 1502 material is etched away using an O₂plasma ash etching technique and removed with a vacuum pump.

With reference additionally now to FIG. 19, a side view ofrepresentative process of the invention is again illustrated and showsthe addition of a layer of ferroelectric material to the F-RAM structure1800, creating F-RAM PZT structure 1900. In FIG. 19, a conformalferroelectric layer of PZT 1902, which may be ideally doped with PZT(lead zirconium titanate), is CVD deposited and planarized on top of thetrench cap 1302, the top of the oxide 202 layer and into the F-RAMopening 402 to a thickness of about 2000 to 3000 angstroms. Thethickness of the PZT 1902 on the sidewalls adjoining the BE spacers 902may be about 400 to 2000 angstroms. The PZT 1902 material is formed oflead (Pb), zirconium (Zr), and titanate (Ti) atoms, with an atomic ratioof the Zr atoms to the Ti atoms (Zr:Ti) of less than 2:3. While PZT 1902is used as the ferroelectric layer, other known ferroelectric compoundssuch as strontium bismuth tantalate (SET) may also be employed.

FIG. 19 also shows a platinum 1904 top electrode (TE) conformal layerthat is subsequently deposited, using CVD, over the top of the PZT 1902ferroelectric layer to a thickness of about 500 to 1000 angstroms. Othersuitable materials for the top electrode (TE) layer include iridium (Ir)and iridium oxide (IrOx), palladium (Pd) and palladium oxide (PdOx),ruthenium (Ru) and ruthenium oxide (RuOx), rhodium (Rh) and rhodiumoxide (RhOx) and other compatible noble metals.

With reference additionally now to FIG. 20, the removal of a portion ofthe CVD platinum TE layer from the F-RAM PZT structure 1900, is shownforming F-RAM structure with platinum TE spacers 2000. In FIG. 20, theplatinum 1904 (FIG. 19) TE conformal layer is etched away from the topof the PZT 1902 layer with a directional reactive-ion etch, forming aset of platinum TE spacers 2002. Note that in this step, the platinum1904 layer remains only along the sides and bottom of the F-RAM opening402.

With reference additionally now to FIG. 21, a top plan view of theinvention is illustrated and depicts the F-RAM opening structure 2100.From a top view perspective, FIG. 21 shows the addition of the platinumTE spacers 2002 and the PZT 1902 ferroelectric layer around the F-RAMopening 402. FIG. 21 also shows the Ti/TiN 106 liners in contact stud A110 and contact stud B 112, and the CVD tungsten 104 filling bothcontact stud A 110 and contact stud B 112. FIG. 21 shows the deposition,on top of the F-RAM opening 402 structure, of a photoresist 2102material that is then imaged to form image opening 2104.

With reference additionally now to FIG. 22, the etching of the platinumTE spacers around the sidewalls on the F-RAM opening structure 2100 isdepicted to create an etched platinum TE spacers structure 2200. In FIG.22, using the pattern defined by the image opening 2104, a portion ofthe platinum TE spacers 2002 around the sidewalls of the F-RAM opening402 is isotropically etched back, forming undercut regions 2202.

With reference additionally now to FIG. 23, the removal of thephotoresist material from the etched platinum TE spacers structure 2200is shown, creating sidewall capacitors structure 2300. In FIG. 23, justthe remaining photoresist 2102 material is etched away using an O₂plasma ash etching technique and removed with a vacuum pump. Note inFIG. 23, the PZT 1902 ferroelectric layer isolates the platinum TEspacers 2002 (top electrode) and the platinum BE spacers 902 (bottomelectrode) to form two sidewall capacitor structures, one on each sideof the F-RAM opening 402, and on top of contact stud A 110 and contactstud B 112.

With reference additionally now to FIG. 24, the application of anon-erodible mask over the sidewall capacitors structure 2300 is shown,forming the contact non-erodible mask structure 2400. An oxide 2402layer is conformably deposited and planarized on top of the PZT 1902ferroelectric layer and into the F-RAM opening 402. A non-erodible maskstructure 2404 is subsequently defined using a photoresist which isimaged and etched to form opening J 2406, opening K 2408, and opening L2410 in the non-erodible mask structure 2404, leaving exposed regions onthe oxide 2402 layer. This non-erodible mask can be made of differentmaterials such as aluminum oxide (Al₂O₃), silicon nitride (Si₃N₄), andother metals such as aluminum.

With reference additionally now to FIG. 25, the etching of the oxide inthe contact non-erodible mask structure 2400 is shown, creating thecontact oxide etching structure 2500. In accordance with thenon-erodible mask 2404 pattern, the exposed regions of oxide 2402 layerin the opening J 2406 and opening K 2408 are etched down below the levelof the PZT 1902 ferroelectric layer using CF₄ in oxygen, creating TEcontact region A 2502 (top electrode) and TE contact region B 2504 (topelectrode). Note that in this process step, etching is also performed onthe opening L 2410 through the PZT 1902 ferroelectric layer and downinto a portion of the oxide 202 layer.

With reference additionally now to FIG. 26, the application of aphotoresist mask over the contact etched structure 2500 is shown,creating photoresist mask structure 2600. In FIG. 26, a photoresist mask2602 is deposited over the contact oxide etched structure 2500 and thenimaged and developed to form an open region X 2604 which is somewhatlarger than the opening L 2410. Note that in this step, the photoresistmask 2602 covers opening J 2406 and opening K 2408.

With reference additionally now to FIG. 27, the etching of the exposedoxide in the photoresist mask structure 2600 is shown, forming etchedoxide structure 2700. According to the pattern created by thephotoresist mask 2602, the oxide 202 material is etched completely downto the contact stud C 114. This oxide 202 material can be removed usinga reactive-ion process. This step creates contact hole Y 2702 and leavescontact stud C 114 exposed.

With reference additionally now to FIG. 28, the removal of thephotoresist mask in the etched oxide structure 2700 is illustrated,forming F-RAM contact opening structure 2800. In FIG. 28, thephotoresist mask 2602 is removed using the same O₂ plasma ash etchingtechnique used in prior steps. Additionally, in FIG. 28, thenon-erodible mask pattern 2404 is subsequently removed employing an ionetch chemistry, specific to the type of materials used in thenon-erodible mask itself. For example, if the non-erodible mask is madeof Si₃N₄, it may be etched by a Si₃N₄ reactive-ion etch that will notaffect the oxide 2402 layer, the Ti/TiN 106 or the CVD tungsten 104 thatare exposed to the etching reactive agent. This step leaves opening J2406, opening K 2408, and opening L 2410 uncovered.

With reference additionally now to FIG. 29, the formation of contactstuds in the F-RAM contact opening structure 2800 is illustrated,creating the final F-RAM contact stud structure 2900. The last processsteps are illustrated in FIG. 29. Ti/TiN 2902 liners are deposited intoopening J 2406, opening K 2408, and opening L 2410 followed by anapplication of a CVD tungsten 2904 layer over the entire surface ofF-RAM contact stud structure 2900, followed by a CMP process to polishback and planarize the CVD tungsten 2904 back to the level of the oxide2402 layer.

As a result, three new contact studs (contact stud J 2906, contact studK 2908 and contact stud L 2910) are formed of Ti/TiN and CVD tungstenand this last step forms the contacts for each of the sidewallcapacitors. Note in FIG. 29, sidewall capacitor 1 2918 (dotted sectionon the left of the F-RAM opening 402) couples the top electrode withcontact stud J 2906 via TE contact region A 2502, and couples the bottomelectrode of the sidewall capacitor with contact stud A 110 through theBE contact region A 2912. Similarly, sidewall capacitor 2 2920 (dottedsection on the right of the F-RAM opening 402) couples the top electrodewith contact stud K 2908 through the TE contact region B 2504, andcouples the bottom electrode of the sidewall capacitor with contact studB 112 via BE contact region B 2914. Notice too that the PZT 1902 layeris common to both sidewall capacitors, in terms of the structures, butthe top electrodes and bottom electrodes are isolated from each other.Also in FIG. 29, contact stud L 2910 (third formed contact stud) iscoupled to contact stud C 114 through contact region 2916.

With reference additionally now to FIG. 30, a top plan view of the F-RAMfinal contact stud structure 3000 is shown. From a top view perspective,FIG. 30 illustrates (as circles) both contact stud J 2906 and contactstud K 2908 formed of Ti/TiN 2902 liners and filled by CVD tungsten 2904at both sides of the F-RAM opening 402. The TE contact region A 2502(top electrode) couples with top contact stud J 2906, while TE contactregion B 2504 (top electrode) couples with top contact stud K 2908.

While there have been described above the principles of the presentinvention in conjunction with specific processing steps and devicestructure, it is to be clearly understood that the foregoing descriptionis made only by way of example and not as a limitation to the scope ofthe invention. Particularly, it is recognized that the teachings of theforegoing disclosure will suggest other modifications to those personsskilled in the relevant art. Such modifications may involve otherfeatures which are already known per se and which may be used instead ofor in addition to features already described herein. Although claimshave been formulated in this application to particular combinations offeatures, it should be understood that the scope of the disclosureherein also includes any novel feature or any novel combination offeatures disclosed either explicitly or implicitly or any generalizationor modification thereof which would be apparent to persons skilled inthe relevant art, whether or not such relates to the same invention aspresently claimed in any claim and whether or not it mitigates any orall of the same technical problems as confronted by the presentinvention. The applicants hereby reserve the right to formulate newclaims to such features and/or combinations of such features during theprosecution of the present application or of any further applicationderived therefrom.

As used herein, the terms “comprises”, “comprising”, or any othervariation thereof, are intended to cover a non-exclusive inclusion, suchthat a process, method, article, or apparatus that comprises arecitation of certain elements does not necessarily include only thoseelements but may include other elements not expressly recited orinherent to such process, method, article or apparatus. None of thedescription in the present application should be read as implying thatany particular element, step, or function is an essential element whichmust be included in the claim scope and THE SCOPE OF THE PATENTEDSUBJECT MATTER IS DEFINED ONLY BY THE CLAIMS AS ALLOWED. Moreover, noneof the appended claims are intended to invoke paragraph six of 35 U.S.C.Sect. 112 unless the exact phrase “means for” is employed and isfollowed by a participle.

1.-43. (canceled)
 44. A method comprising: forming an opening in aninsulating layer over a surface of a substrate; forming bottom electrodespacers proximal to sidewalls of the opening; forming a ferroelectricdielectric layer in the opening over the surface of the substrate andbetween the bottom electrode spacers; and forming a pair of topelectrodes within the opening comprising first and second side portionsdisplaced laterally from respective ones of the bottom electrode spacersby the ferroelectric dielectric layer.
 45. The method of claim 44further comprising: forming an additional insulating layer between thetop electrodes and over the ferroelectric dielectric layer; and formingfirst and second contacts to respective ones of the pair of topelectrodes within the additional insulating layer.
 46. The method ofclaim 44 wherein forming the opening in the insulating layer comprisesselectively removing a portion of the insulating layer to exposeportions of at least two contact studs in the surface of the substrate.47. The method of claim 46 wherein forming bottom electrode spacerscomprises forming bottom electrode spacers electrically coupling torespective ones of the at least two contact studs.
 48. The method ofclaim 47 further comprising forming an insulating cap in a lower portionof the opening prior to forming the ferroelectric dielectric layer, andwherein forming the ferroelectric dielectric layer in the openingcomprises forming the ferroelectric dielectric layer in the opening overthe insulating cap and between the bottom electrode spacers.
 49. Themethod of claim 48 wherein the opening comprises selectively removing aselected region of the surface of the substrate, and wherein forming theinsulating cap comprises filling the selected region of the surface ofthe substrate.
 50. The method of claim 46 further comprising formingfirst spacers adjoining sidewalls of the opening over the at least twocontact studs prior to forming the bottom electrode spacers, and whereinforming the bottom electrode spacers comprises forming the bottomelectrode spacers, each contacting respective ones of the at least twocontact studs in the opening and adjoining the first spacers.
 51. Themethod of claim 50 wherein forming first spacers and the bottomelectrode spacers comprises: depositing a conformal first spacer layerin the opening to conform to sidewalls and a lower surface of theopening; depositing a bottom electrode layer over the conformal firstspacer layer; and etching the bottom electrode layer and the conformalfirst spacer layer to form the first spacers and the bottom electrodespacers.
 52. A method comprising: forming an opening in an insulatinglayer over a surface of a substrate to expose portions of at least twocontact studs in the surface of the substrate; forming bottom electrodespacers proximal to sidewalls of the opening and electrically couplingto respective ones of the at least two contact studs. forming aferroelectric dielectric layer in the opening over the surface of thesubstrate and between the bottom electrode spacers; forming a pair oftop electrodes within the opening comprising first and second sideportions displaced laterally from respective ones of the bottomelectrode spacers by the ferroelectric dielectric layer; forming anadditional insulating layer between the top electrodes and over theferroelectric dielectric layer; and forming first and second contacts torespective ones of the pair of top electrodes within the additionalinsulating layer.
 53. The method of claim 52 further comprising formingan insulating cap in a lower portion of the opening prior to forming theferroelectric dielectric layer, and wherein forming the ferroelectricdielectric layer in the opening comprises forming the ferroelectricdielectric layer in the opening over the insulating cap and between thebottom electrode spacers.
 54. The method of claim 53 wherein the openingcomprises selectively removing a selected region of the surface of thesubstrate, and wherein forming the insulating cap comprises filling theselected region of the surface of the substrate.
 55. The method of claim52 further comprising forming first spacers adjoining sidewalls of theopening over the at least two contact studs prior to forming the bottomelectrode spacers, and wherein forming the bottom electrode spacerscomprises forming the bottom electrode spacers, each contactingrespective ones of the at least two contact studs in the opening andadjoining the first spacers.
 56. The method of claim 55 wherein formingfirst spacers and the bottom electrode spacers comprises: depositing aconformal first spacer layer in the opening to conform to sidewalls anda lower surface of the opening; depositing a bottom electrode layer overthe conformal first spacer layer; and etching the bottom electrode layerand the conformal first spacer layer to form the first spacers and thebottom electrode spacers.
 57. A method comprising: forming an opening inan insulating layer over a surface of a substrate selectively removing aportion of the insulating layer and a selected portion of the surface toform an opening extending to and partially between at least two contactstuds in the surface of the substrate; forming first spacers adjoiningsidewalls of the opening over the at least two contact studs; formingbottom electrode spacers adjoining the first spacers and electricallycoupling to respective ones of the at least two contact studs; formingan insulating cap in a lower portion of the opening; forming aferroelectric dielectric layer in the opening over the insulating capand between the bottom electrode spacers; and forming a pair of topelectrodes within the opening comprising first and second side portionsdisplaced laterally from respective ones of the bottom electrode spacersby the ferroelectric dielectric layer.
 58. The method of claim 57further comprising: forming an additional insulating layer between thetop electrodes and over the ferroelectric dielectric layer; and formingfirst and second contacts to respective ones of the pair of topelectrodes within the additional insulating layer.
 59. The method ofclaim 57 wherein forming first spacers and forming the bottom electrodespacers comprises: depositing a conformal first spacer layer in theopening to conform to sidewalls and a lower surface of the opening;depositing a bottom electrode layer over the conformal first spacerlayer; and etching the bottom electrode layer and the conformal firstspacer layer to form the first spacers and the bottom electrode spacers.60. The method of claim 59 wherein etching the bottom electrode layerand the conformal first spacer layer comprises anisotropically etchingthe bottom electrode layer and the conformal first spacer layer usingreactive ion etching (RIE).
 61. The method of claim 59 wherein theconformal first spacer layer comprises titanium aluminum nitride. 62.The method of claim 59 wherein a bottom electrode layer comprises atleast one of Pt, Ir, IrOx, Pd, PdOx, Ru, RuOx, Rh, RhOx or other noblemetal.
 63. The method of claim 57 wherein forming the insulating capcomprises filling the selected portion of the surface between the atleast two contact studs in the surface of the substrate and coveringexposed portions of the at least two contact studs.